So-called start/stop systems are becoming increasingly common in motor vehicles powered by internal combustion engines. These systems offer improved fuel efficiency, especially during stop-and-go driving in congested traffic areas. This is primarily due to a shut-off of the internal combustion engine when not required to propel the vehicle and a restart thereof once required again.
A consideration with shut-off of the internal combustion engine while various vehicle electrical systems are running is that the voltage of the vehicle electrical systems may drop below battery voltage, accounting also for the voltage drop in the cable harness of the vehicle.
Such a drop in the vehicle electrical system voltage may potentially cause problems for vital electrical systems of the vehicle, e.g. exterior lighting systems and possibly also chassis systems.
To deal with this issue, some known current start/stop solutions incorporate a large main battery, such as a conventional acid-lead battery, and a smaller-size support battery. The support battery in such a known arrangement is arranged to supply the vehicle electrical system during warm-starts of the engine. A warm-start is the restarting of the engine that occurs after a relatively brief shut-down period, as during normal start/stop operation of the vehicle while driving.
However, such a known arrangement suffers from limitations in the case of an increased number of start/stop events, higher timing demands and increased current consumption by various vehicle systems.